Garner, R, Mihos, JC, Hardng, P and Watkins, AE (2021) A Deep Census of Outlying Star Formation in the M101 Group. ASTROPHYSICAL JOURNAL, 915 (1). ISSN 0004-637X

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Abstract

We present deep, narrowband imaging of the nearby spiral galaxy M101 and its group environment to search for star-forming dwarf galaxies and outlying H ii regions. Using the Burrell Schmidt telescope, we target the brightest emission lines of star-forming regions, Hα, Hβ, and [O iii], to detect potential outlying star-forming regions. Our survey covers ∼6 deg2 around M101, and we detect objects in emission down to an Hα flux level of 5.7 10-17 erg s-1 cm-2 (equivalent to a limiting star formation rate of 1.7 10-6 M o˙ yr-1 at the distance of M101). After careful removal of background contaminants and foreground M stars, we detect 19 objects in emission in all three bands and 8 objects in emission in Hα and [O iii]. We compare the structural and photometric properties of the detected sources to Local Group dwarf galaxies and star-forming galaxies in the 11HUGS and SINGG surveys. We find no large population of outlying H ii regions or undiscovered star-forming dwarfs in the M101 Group, as most sources (93%) are consistent with being M101 outer-disk H ii regions. Only two sources were associated with other galaxies: a faint star-forming satellite of the background galaxy NGC 5486 and a faint outlying H ii region near the M101 companion NGC 5474. We also find no narrowband emission associated with recently discovered ultradiffuse galaxies and starless H i clouds near M101. The lack of any hidden population of low-luminosity star-forming dwarfs around M101 suggests a rather shallow faint-end slope (as flat as α ∼ -1.0) for the star-forming luminosity function in the M101 Group. We discuss our results in the context of tidally triggered star formation models and the interaction history of the M101 Group.

Item Type:	Article
Uncontrolled Keywords:	Astronomy & Astrophysics; COMA CLUSTER; DWARF GALAXIES; FORMATION THRESHOLDS; H-II REGIONS; HII-REGIONS; INTRAGROUP MEDIUM; LUMINOSITY FUNCTION; Physical Sciences; Science & Technology; SURFACE BRIGHTNESS; ULTRADIFFUSE GALAXIES; ULTRA-DIFFUSE GALAXIES; Science & Technology; Physical Sciences; Astronomy & Astrophysics; ULTRA-DIFFUSE GALAXIES; H-II REGIONS; DWARF GALAXIES; SURFACE BRIGHTNESS; INTRAGROUP MEDIUM; HII-REGIONS; ULTRADIFFUSE GALAXIES; FORMATION THRESHOLDS; LUMINOSITY FUNCTION; COMA CLUSTER; astro-ph.GA; astro-ph.GA; 0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); Astronomy & Astrophysics
Subjects:	Q Science > QB Astronomy
Divisions:	Astrophysics Research Institute
Publisher:	IOP PUBLISHING LTD
SWORD Depositor:	A Symplectic
Date Deposited:	07 Oct 2022 12:40
Last Modified:	07 Oct 2022 12:45
DOI or ID number:	10.3847/1538-4357/ac0055
URI:	https://researchonline.ljmu.ac.uk/id/eprint/17759

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